The invention relates to multilayer panels for use as wall coverings, space dividers, or ceiling panels with improved acoustics.
Multilayer panels are used in the construction of conveyances, such as ships and passenger trains and aircraft, as cabin dividers, wall coverings or wall linings and as ceiling panels. Multilayer panels have a core enclosed between at least two cover layers. The core is either a foam structure or a honeycomb structure with empty or foam-filled honeycomb cells that may have different cross-sectional configurations. The cores may also be multilayer laminated structures. The cover layers are made of materials having a high tensile strength. Conventional panels do not have satisfactory acoustic characteristics. More specifically, such panels have a low noise transmission loss, and a high structure borne noise radiation.
The prior art discussed below does not show efforts to solve these problems in combination.
German Patent Publication DE 41 26 781 A1 discloses multilayer panels constructed as described above. The panels are provided with straight parallel slots in the core for improving the pliability or flexibility or bendability in one direction. The slots have a defined width, a uniform slot spacing, and the slot depth ranges from 80 to 95% of the core thickness to form a lightweight, bendable panel. Such lightweight panels are quite flexible, but their acoustic characteristics leave room for improvement.
German Patent Publication 195 27 081 C1 discloses a lightweight construction panel, for example for making roll-up doors, that must be flexible in opposite directions. For this purpose two slotted panels are combined. Each panel is constructed as described above with a core, two cover layers and straight slots in the core. An intermediate layer between the two combined panels improves a relative sliding ability between the two assembled panels. Acoustic characteristics are neither mentioned nor suggested.
A panel construction similar to the above described panels is disclosed in German Patent Publication DE 100 34 990 A1 in which the slots extend in two directions in the core, thereby forming a slotted rectangular grid structure in the core, without penetrating the core, for improving the acoustic characteristics, particularly for reducing noise radiations.
The above described conventional panels have a mechanical strength problem, because cracks and even breaks occur quite often, presumably due to the straight slots. Specifically, the cover layer positioned on the compression side of a bent panel breaks easily in response to bending, whereby the respective cover layer breaks into one or more slots. This phenomenon is known as xe2x80x9ctrench breakxe2x80x9d which must be avoided.
In view of the foregoing it is the aim of the invention to achieve the following objects singly or in combination:
to improve the acoustic characteristics of lightweight construction panels by increasing their noise transmission loss and decreasing their structure borne noise radiation.
to avoid the above mentioned trench breaks in acoustically improved lightweight construction panels;
to improve the acoustic characteristics of the panels by using slots in the core without decreasing the crash load capacity of the panel; and
to form slot configurations and slot patterns in the core of the panel for improving the acoustic panel characteristics without impairing the strength of these panels.
According to the invention there is provided a multilayer panel comprising a core having first and second base surfaces, at least a first ply covering said first base surface and at least one second ply covering said second base surface, a first plurality of curved slots extending in a first direction in said core, a second plurality of curved slots extending in a second direction in said core, said first and second directions crossing each other at angles other than right angles, and wherein said first plurality of curved slots and said second plurality of curved slots comprise curvatures curved in space, so that first slots of said first plurality of slots have a first spacing from one another, so that second slots of said second plurality of slots have a second spacing from each other, and so that said first and second slots have a varying slot depth within said core.
An important advantage of the invention is seen in that lightweight panels constructed as taught herein achieve simultaneously, in addition to their light weight, two desirable features, namely an acceptable mechanical strength in spite of having a slotted core and desirable acoustic characteristics. Conventional straight slots that cross each other are good for improving acoustic characteristics, but bad with regard to mechanical panel characteristics. The invention solves this problem by avoiding conventionally shaped slots in the present panels with specially curved slots, slot configurations and slot patterns in the panel cores.